Preheat oven to 325°. Cook lemon slices in a medium saucepan of boiling water 2 minutes to remove bitterness. Drain and pat dry.
Gently toss lemon slices with sage, sugar, and 1 tablespoon oil in a medium bowl. Spread out on a parchment-lined baking sheet and bake until lemons are no longer wet and only slightly colored, 15–20 minutes. Let cool.
Whisk pomegranate molasses, allspice, and remaining 1 tablespoon oil in a large bowl; season with salt and pepper. Add lemons, tomatoes, onion, parsley, mint, and sprouts, if using, and toss gently; season with salt and pepper.